1. Field of the Invention
The invention relates generally to compositions and methods for influencing recovery from strenuous physical activity and particularly to compositions comprising carbohydrates, amino acids, or antioxidants and the use of such compositions to influence recovery from strenuous physical activity in animals.
2. Description of Related Art
Physical exhaustion in animals results from physical activity depending on intensity and/or duration. Strenuous activities, including work, sports, exercise, and the like have the potential to produce the physical or biochemical changes associated with physical exhaustion. For some animals, activities like hunting, tracking, sled racing, agility trials, and play activities can lead to physical exhaustion. Other activities, such as parturition in pregnant animals, and excessive non-specific activities like temporary placement in a kennel facility can also result in physical exhaustion. Physical exhaustion is associated with a variety of physical, cellular and biochemical changes, beginning with depletion of muscle and liver glycogen stores. Liver glycogen is a source of glucose for cellular function in the muscle, brain, and other tissues required to support bouts of exercise or physical activity.
Such physical activity and depletion of glycogen are also associated with muscle-fiber damage, muscle soreness, muscle inflammation, and/or fatigue. This damage results, at least in part, from the disruption of cell membrane integrity and subsequent cell content leakage, along with damage from oxidative stress. Elevated levels of creatine kinase (CK, also known as creatine phosphokinase or CPK)) and lactate dehydrogenase (LDH) following exercise are hallmark indicators of activity-induced muscle-fiber damage and disruption of muscle membrane integrity. Strenuous or excessive physical activity is also associated with an elevation of lactic acid that additionally contributes to muscle soreness (for example, delayed-onset muscle soreness) and fatigue.
Products are available that address the problem of replenishing exercise-depleted glycogen stores with carbohydrates to improve exercise recovery, see WO 2004/077961. However, studies in humans have demonstrated that dietary supplementation of carbohydrates alone after exercise cannot improve recovery from muscle damage.
Strenuous physical activity such as exercise also results in a significant amount of oxidative stress. It is known that inflammation and oxidative stress are linked via muscle metabolism and muscle damage, particularly during exercise. Because oxidative stress and inflammation have traditionally been associated with fatigue and impaired recovery from exercise, research has focused on nutritional strategies aimed at reducing these effects. Currently, antioxidants such as vitamins E and C are widely recommended to attenuate the effects of exercise-induced oxidative stress. However, alternative antioxidants are needed because both vitamins C and E can act as pro-oxidants under certain conditions. Pro-oxidants enhance rather than reduce the formation of reactive oxygen and nitrogen species.
Studies in greyhounds have demonstrated a decrease in performance with vitamin E dietary supplementation. Other studies have shown that sled dogs administered diets supplemented with vitamin E and vitamin C showed no improvement in post-exercise indices of oxidative stress when compared to sled dogs given no antioxidant supplements. WO2004077961 discloses methods and composition for helping animals recover from the results of strenuous activity. The methods entail administering a composition comprising a mixture of carbohydrates to provide readily assimilated or available energy, such as glucose, a source of vitamins, minerals, and antioxidants that are expended more quickly during the strenuous activity than at other times, or required in response to the demands of the activity.
There is, however, a need for new compositions and methods that influence recovery from strenuous physical activity in animals, e.g., exercise recovery.